Method and apparatus for geo-locating mobile station

ABSTRACT

A method for estimating a geographic location of a mobile station includes calculating an angular position of a mobile station to a base station based on first and second signal strength measurements and an angular position reference for the base station, the signal strength measurements from the mobile station for RF signals from first and second sector antennas of the base station. Another method includes calculating a radial distance of a mobile station from a base station serving the mobile station, determining a signal strength report from the mobile station includes a signal strength measurement for an RF signal from a first sector antenna of the base station, and identifying a geographic location of the mobile station based on intersection of a circle around the base station with a radius of the radial distance with a sub-sector geographic area in an RF coverage map for the first sector antenna.

BACKGROUND

This disclosure relates to providing wireless service to a mobilestation in a wireless network and more particularly, but notexclusively, to estimating a geographic location for a mobile stationwithin a coverage area of a wireless network.

Geographic location information for mobile stations has tremendous valueto mobile applications, network optimization (e.g., self optimizednetwork (SON)), capacity management, and drive test substitutions, etc.Although many modern mobile stations can obtain their own locations fromintegrated GPS modules, it is still a challenge for the network to trackthe locations of a large number of subscribers for an extended period oftime. A frequent location update from mobile stations would increasenetwork overhead and may overwhelm the network and create bottlenecks. Apassive location estimation technique that leverages measurements fromnormal network operation is desirable because it avoids such increasesin network overhead.

For example, in third generation (3G) code division multiple access(CDMA) networks, such as 3G1X, EVDO, UMTS, etc., one can triangulate thegeographic location of a mobile station from the reported round tripdelays between the mobile station and three or more base stations (seeFIG. 1). The corresponding round trip delays are sent back by the mobilestations for call processing, thus no additional signaling overhead isincurred by the network to collect measurements for triangulation.

However, this triangulation approach does not work in all networks, suchas the fourth generation (4G) long term evolution (LTE) networks. Unlike3G CDMA networks, each measurement report in LTE networks only containsthe round trip delay from one cell (i.e., the serving cell of themobile). Thus, the triangulation technique cannot be used at all inconjunction with 4G LTE networks.

Additionally, geographic location information for mobile stations hastremendous value in compilation and formulation of RF coverage maps forwireless networks. RF coverage maps are useful for management of thenetwork infrastructure and the wireless services provided to users andsubscribers. For example, RF coverage maps may be useful to networkoperators and service providers for troubleshooting and planning formaintenance and upgrades.

However, most of the RF coverage maps are obtained through drive tests.Accurate RF coverage map take hours of drive tests and are very costly.Moreover, as network evolve and environment changes, such as adding newcells or new building construction, the drive tests have to be redone tokeep the coverage information up to date. Thus, maintenance of RFcoverage maps using drive testing adds even more to the cost.

For these and other reasons, there is a need to provide a technique forestimating a geographic location of a mobile station for at least 4G LTEnetworks. Additionally, it is desirable that the technique be compatiblewith other types of wireless networks, especially 3G CDMA networks. Itis also desirable that the technique be more reliable than thetriangulation technique. Additionally, it is desirable that thetechnique for estimating a geographic location of a mobile stationsupport construction or maintenance of RF coverage maps in a more costeffective manner than the drive testing technique.

SUMMARY

In one aspect, a method for estimating a geographic location of a mobilestation within a coverage area of a wireless network is provided. In oneembodiment, the method includes: calculating an instant angular positionof an individual mobile station in relation to a first base station, thefirst base station including multiple sector antennas, the instantangular position based at least in part on a first signal strengthmeasurement, a second signal strength measurement, and an angularposition reference that extends outward from the first base station, thefirst and second signal strength measurements related in calendar timeand representative of power characteristics of respective radiofrequency (RF) signals received by the individual mobile station fromcorresponding first and second sector antennas of the first basestation.

In another embodiment, a method for estimating a geographic location ofa mobile station within a coverage area of a wireless network includes:calculating a radial distance of an individual mobile station from afirst base station serving the individual mobile station, the first basestation including multiple sector antennas, the radial distance based atleast in part on a round trip measurement associated with elapsed timebetween sending an outgoing signal from the first base station to theindividual mobile station and receiving a corresponding acknowledgementsignal from the individual mobile station at the first base station;determining a signal strength report from the individual mobile stationprovided to the first base station related in calendar time to the roundtrip measurement includes a first signal strength measurementrepresentative of a power characteristic of a first radio frequency (RF)signal received by the individual mobile station from a first sectorantenna of the first base station, the signal strength report notincluding other signal strength measurements for other sector antennasof the first base station; and identifying an instant geographiclocation of the individual mobile station in a coverage area of awireless network formed by at least the first base station, the instantgeographic location based at least in part on an intersection of acircle having a center defined by the first base station and a radiusdefined by the radial distance with a first sub-sector geographic areain a first RF coverage map for the first sector antenna, the first RFcoverage map including a first reference location for the first basestation to facilitate correlation of the circle to the first RF coveragemap, the first RF coverage map formed by a plurality of sub-sectorgeographic areas, the first RF coverage map populated withrepresentative RF coverage levels associated with previous signalstrength measurements for the first sector antenna from one or moremobile stations in previous signal strength reports comprising thecorresponding previous signal strength measurement and at least onesignal strength measurement from another sector antenna of the firstbase station, wherein the first sub-sector geographic area in the firstRF coverage map is populated with a first RF coverage levelrepresentative of lacking previous signal strength measurements.

In yet another embodiment, a method for estimating a geographic locationof a mobile station within a coverage area of a wireless networkincludes: calculating a radial distance of an individual mobile stationfrom a first base station serving the individual mobile station inresponse to detection of a dropped call for the mobile station, thefirst base station including multiple sector antennas, the radialdistance based at least in part on a round trip measurement precedingdetection of the dropped call and in proximate time relation todetection of the dropped call, the round trip measurement associatedwith elapsed time between sending an outgoing signal from the first basestation to the individual mobile station and receiving a correspondingacknowledgement signal from the individual mobile station at the firstbase station; determining a signal strength report from the individualmobile station provided to the first base station preceding detection ofthe dropped call, in proximate time relation to detection of the droppedcall, and related in calendar time to the round trip measurementincludes a first signal strength measurement representative of a powercharacteristic of a first radio frequency (RF) signal received by theindividual mobile station from a first sector antenna of the first basestation; and identifying an instant geographic location of theindividual mobile station in a coverage area of a wireless networkformed by at least the first base station, wherein identification of theinstant geographic location is based at least in part on an intersectionof a circle having a center defined by the first base station and aradius defined by the radial distance with a first sub-sector geographicarea in a first RF coverage map for the first sector antenna, the firstRF coverage map including a first reference location for the first basestation to facilitate correlation of the circle to the first RF coveragemap, the first RF coverage map formed by a plurality of sub-sectorgeographic areas, the first RF coverage map populated withrepresentative RF coverage levels associated with previous signalstrength measurements for the first sector antenna from one or moremobile stations in previous signal strength reports, wherein the firstsub-sector geographic area in the first RF coverage map is populatedwith an RF coverage level representative of a first signal strengthvalue within a first predetermined threshold of the first signalstrength measurement.

In another aspect, an apparatus for estimating a geographic location ofa mobile station within a coverage area of a wireless network isprovided. In one embodiment, the apparatus includes: a distance moduleand an angular position module.

In yet another aspect, a non-transitory computer-readable medium storingprogram instructions is provided. The program instructions, whenexecuted by a computer, cause a corresponding computer-controlled deviceto perform a method for estimating a geographic location of a mobilestation within a coverage area of a wireless network.

Further scope of the applicability of this the present invention willbecome apparent from the detailed description provided below. It shouldbe understood, however, that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art.

DESCRIPTION OF THE DRAWINGS

The present invention exists in the construction, arrangement, andcombination of the various parts of the device, and steps of the method,whereby the objects contemplated are attained as hereinafter more fullyset forth, specifically pointed out in the claims, and illustrated inthe accompanying drawings in which:

FIG. 1 is a functional diagram showing three cells of a wireless networkin relation to an exemplary embodiment of a triangulation technique forestimating the geographic location of a mobile station;

FIG. 2 is a functional diagram showing a serving cell of a wirelessnetwork in relation to an exemplary embodiment of another technique forestimating the geographic location of a mobile station;

FIG. 3 is a graph showing a transmit antenna gain characteristic for asector antenna of a base station in which normalized gain in dB isplotted in relation to look angles from the sector antenna to a mobilestation in relation to azimuth (i.e., horizontal gain) and elevation(i.e., vertical gain) positions from the orientation of the sectorantenna;

FIG. 4 is a flow chart of an exemplary embodiment of a process forestimating a geographic location of a mobile station within a coveragearea of a wireless network;

FIG. 5, in combination with FIG. 4, is a flow chart of another exemplaryembodiment of a process for estimating a geographic location of a mobilestation within a coverage area of a wireless network;

FIG. 6 is a block diagram of an exemplary embodiment of an apparatuswithin a serving base station of a wireless network for estimating ageographic location of a mobile station within a coverage area of thewireless network;

FIG. 7 is a block diagram of an exemplary embodiment of an apparatuswithin a geo-location service node of a wireless network for estimatinga geographic location of a mobile station within a coverage area of thewireless network;

FIG. 8 is a block diagram of an exemplary embodiment of an apparatuswithin a network management node associated with a wireless network forestimating a geographic location of a mobile station within a coveragearea of the wireless network;

FIG. 9 is a block diagram of an exemplary embodiment of an angularposition module associated with the apparatus shown in FIGS. 6-8;

FIG. 10 is a flow chart of an exemplary embodiment of a process forestimating a geographic location of a mobile station within a coveragearea of a wireless network performed by a computer-controlled deviceexecuting program instructions stored on a non-transitorycomputer-readable medium;

FIG. 11 is a bird's eye view of a coverage area of an exemplary basestation in a wireless network showing an estimated geographic locationand a GPS location for a mobile station;

FIG. 12 is a set of graphs showing azimuth gain parametercharacteristics for two sector antennas of a base station, elevationgain parameter characteristics for the two sector antennas, a compositegraph showing the difference between gains for the two sector antennas,and a graph of a function of the angular position of the mobile stationin relation to the delta antenna gain component, a delta transmitparameter component, and a delta signal strength measurement component;

FIG. 13 is a functional diagram showing three base stations, each withthree sector antennas, in relation to exemplary embodiments of varioustechniques for estimating the geographic location of a mobile station;

FIG. 14 is an example of an RF coverage map for a sector antenna of abase station that is used in relation to an exemplary embodiment of atechnique for estimating the geographic location of a mobile station;

FIG. 15 is another example of an RF coverage map for a sector antenna ofa base station that is updated in conjunction with an exemplaryembodiment of a technique for estimating the geographic location of amobile station;

FIG. 16 is yet another example of an RF coverage map for a sectorantenna of a base station that is used in relation to another exemplaryembodiment of a technique for estimating the geographic location of amobile station;

FIG. 17 is a flow chart of an exemplary embodiment of a process forestimating a geographic location of a mobile station within a coveragearea of a wireless network;

FIG. 18, in combination with FIG. 17, is a flow chart of anotherexemplary embodiment of a process for estimating a geographic locationof a mobile station within a coverage area of a wireless network;

FIG. 19, in combination with FIG. 17, is a flow chart of yet anotherexemplary embodiment of a process for estimating a geographic locationof a mobile station within a coverage area of a wireless network;

FIG. 20 is a flow chart of still another exemplary embodiment of aprocess for estimating a geographic location of a mobile station withina coverage area of a wireless network;

FIG. 21, in combination with FIG. 20, is a flow chart of still yetanother exemplary embodiment of a process for estimating a geographiclocation of a mobile station within a coverage area of a wirelessnetwork;

FIG. 22, in combination with FIG. 20, is a flow chart of anotherexemplary embodiment of a process for estimating a geographic locationof a mobile station within a coverage area of a wireless network; and

FIG. 23 is a flow chart of yet another exemplary embodiment of a processfor estimating a geographic location of a mobile station within acoverage area of a wireless network.

DETAILED DESCRIPTION

Various embodiments of methods and apparatus provide techniques forestimating a geographic location of a mobile station within a coveragearea of a wireless network. In one embodiment, an algorithm estimates ageographic location of mobile station that reports signal strengthmeasurements from multiple sector antennas of a serving base station ina wireless network in which the serving base station reports a roundtrip measurement associated with the mobile station. For example, thevarious embodiments of the geographic location estimating algorithm canbe use to estimate the location of a mobile station in a 4G LTE network.Various embodiments of the algorithm can also estimate the location of amobile station in 3G CDMA wireless networks and other types of wirelessnetworks that use base stations with multiple sector antennas. Thealgorithm provides improved accuracy in estimating location informationfor a mobile station by combining both the distance and signalingstrength/quality reports.

With reference to FIG. 13, a functional diagram shows three basestations, each with three sector antennas, in relation to exemplaryembodiments of various techniques for estimating the geographic locationof a mobile station by dividing the wireless service area into differentcategories of circumstances for estimating the location. Different typesof data are available for the different categories. Thus, the techniquesfor estimating geographic location are adjusted for each category basedon the type of data available under the corresponding circumstance.

In a category 1 area, mobile station locations can be determined by analgorithm that calculates an angular position of the mobile station inrelation to a serving or neighboring base station using signal strengthmeasurements from multiple sector antennas of the base station in ameasurement report from the mobile station and determines a radialdistance of the mobile station from the serving base station based on around trip measurement. Various embodiments of algorithms for thecategory 1 area are provided below in the descriptions of FIGS. 1-12 and17-19.

With continued reference to FIG. 13, category 2 areas are locations inwhich the mobile station is only receiving signal strength measurementsfrom one sector antenna from each of one, two, or more base stations.Category 2 areas can be viewed as the rest of the coverage area for agiven cell (or given sector) of the wireless network that do not fitunder the category 1 circumstances. In a category 2 area, the mobilestation location is determined based on the combination of determining aradial distance of the mobile station from a serving based station basedon a round trip measurement and a strength measurements from one sectorantenna of each of one, two, or more base stations in a measurementreport from the mobile station to identify potential sub-sectorgeographic coverage areas in an RF coverage map for a serving sectorantenna of the serving base station populated with an RF coverage levelrepresentative of lacking previous signal strength measurements, andusing RF coverage levels in the RF coverage map for neighboringsub-sector geographic coverage areas to estimate the geographic locationof the mobile station. Various embodiments of algorithms for thecategory 1 area are provided below in the descriptions of FIGS. 6-10 and20-22.

With continued reference to FIG. 13, for each sub-sector geographic areain the RF coverage map, a geo-bin is used to store signal strengths forthe corresponding sub-sector geographic area. The RF coverage level forthe sub-sector geographic area is updated over time by averaging (or bytaking a median value) over multiple records of signal strengthmeasurements. Study has shown that the longer the observation period,the more accurate the results are for the corresponding RF coveragelevel. For example, eight hours of signal strength measurements resultsin an RF coverage level that is more accurate than signal strengthmeasurements spanning one hour for the same area.

An exemplary embodiment of techniques for estimating the geographiclocation of a mobile station for category 1 and category 2 circumstancesare described below. RF coverage maps may be built up by taking enoughmeasurement data over a suitable period of time to generate suitableinitial RF coverage maps. For example, taking eight hours of per callmeasurement data (PCMD) in down town busy areas may be used to generatean RF coverage map. The RF coverage maps my be built up from geographiclocations for the mobile stations obtained using the techniquesdescribed herein or by other suitable location determining techniques.

The measurement data may be divided into category 1 and category 2circumstances. Category 1 measurements contain signal strengthmeasurements by the mobile station from the same base station, butdifferent sectors. The rest of the measurement data belongs to category2 circumstances.

Each category may be further divided into sub categories. An example ofhow to generate an initial RF coverage map for base station 1, sector αfor subcategory 1A circumstances is based on the mobile station seeingtwo pilots from different sectors (sector α and sector β) of basestation 1. Both pilots may be used to estimate the mobile stationlocation by using a suitable embodiment of the algorithm disclosedherein. In addition, the pilot from base station1, sector α may also beused to plot an RF coverage map for the corresponding sector α antennabased on category 1A geographic location estimates for the mobilestation.

Similarly, an example of how to generate an initial RF coverage map forbase station 1, sector α for subcategory 1B circumstances is based onthe mobile station seeing two pilots from different sectors (sector βand sector γ) of base station β and one pilot from base station 1,sector α. The two pilots from base station 3, sector β and sector γ areused to estimate the mobile location by using the algorithm disclosedherein. The pilot from base station1, sector α may be used to plot an RFcoverage map for the corresponding sector α antenna based on category 1Bgeographic location estimates for the mobile station.

As for subcategory 2A, the mobile station only sees a single pilot frombase station 1, sector α. Hence, in subcategory 2A circumstances, themobile station is around a bore sight area for base station 1, sector αwhere it is most likely that only one pilot is seen by the mobilestation. Here, the mobile station location is estimated by using thepilot information, distance information, and RF coverage levels andcorresponding geo-bin information for sub-sector geographic areas thatare neighboring potential sub-sector geographic areas with RF coveragelevels showing that previous signal strength measurements are lacking.With the geographic location for the mobile station identified, thepilot from base station 1, sector α may also be used to supplement (orplot) an RF coverage map of the sector under category 2 circumstances.

As for subcategory 2B, the mobile station sees one pilot from basestation 1, sector α and another pilot from base station 2, sector β.Hence, in subcategory 2B circumstances, the mobile station is around anarea between base station 1 and base station 2. Here, the mobile stationlocation is estimated using both pilots information and distanceinformation combined with RF coverage levels and corresponding geo-bininformation for sub-sector geographic areas that are neighboringpotential sub-sector geographic areas with RF coverage levels showingthat previous signal strength measurements are lacking to get a moreaccurate estimation of the mobile station location. With the geographiclocation for the mobile station identified, the pilot from base station1, sector α may also used to supplement (or plot) an RF coverage map ofthe sector under category 2 circumstances.

With reference to FIG. 14, an example of an RF coverage map for a sectorantenna of a base station is shown that can be used in conjunction withan exemplary embodiment of a technique for estimating the geographiclocation of a mobile station. In various exemplary embodiments oftechniques for estimating the geographic location of a mobile station,the category 1 measurements can be used to build category 1 RF coveragemaps (including measurements associated with subcategory 1A andsubcategory 1B circumstances). Various embodiments of the algorithm toobtain mobile station geographic location in category 1 circumstances isdescribed in more detail below in the descriptions of FIGS. 1-12 and17-19.

With continued reference to FIGS. 14 and 15, signal strengthmeasurements from category 2 circumstances can be combined with category1 RF coverage maps and/or existing signal strength measurementinformation stored in geo-bins associated with neighboring sub-sectorgeographic areas to generate category 2 RF coverage maps. For example,in FIG. 14, in a category 1 area, including areas for subcategory 1A andsubcategory 1B circumstances, an RF coverage map for base station A,sector 3 is already built from previous category 1 signal strengthmeasurements. The category 1 RF coverage map shows that areas forsubcategory 2A and subcategory 2B for base station A, sector 3 do notcurrently have valid Ec/Io information.

As for subcategory 2A, the mobile station sees a pilot from base stationA, sector 3 with Ec/Io at −5 dB. In the mean time, base station A,sector 3 measured the round trip delay associated with the mobilestation to be equivalent to distance d. In this example, there are twosub-sector geographic areas and corresponding geo-bins that areassociated with the distance d criteria in the area associated withsubcategory 2A circumstances. The technique goes on to determine whichsub-sector geographic area or corresponding geo-bin signal measurementsin the area for subcategory 2A circumstances is associated with themobile station location.

In the embodiment being described, the sub-sector geographic area andcorresponding geo-bin in the base station A, sector 3 area just north ofthe area associated with subcategory 2A circumstances has Ec/Io at −2dB. The sub-sector geographic area and corresponding geo-bin in the basestation A, sector 3 area just south of the area associated withsubcategory 2A circumstances has Ec/Io at −6 dB. In this embodiment, thesouthern sub-sector geographic area and corresponding geo-bin in areaassociated with subcategory 2A circumstances is chosen to indicate themobile station location because the measurement report of pilot Ec/Io at−5 dB is closer to −6 dB than −2 dB. The updated overall RF coverage mapfor base station A, sector 3 is shown in FIG. 15.

With continued reference to FIG. 14, as for subcategory 2B, the mobilestation sees a pilot from base station A, sector 3 with Ec/Io at −7 dBand another pilot from base station B, sector 2. In the mean time, basestation A, sector 3 measured the round trip delay associated with themobile station to be equivalent to distance d. In this example, thereare two sub-sector geographic areas and corresponding geo-bins that areassociated with the distance d in the area associated with subcategory2B measurements. In the embodiment being described, the sub-sectorgeographic areas and corresponding geo-bins neighboring the areasassociated with the category 2B circumstances in the base station A,sector 3 coverage area have pilot Ec/Io signals around −7 dB. The nextstep is to determine which sub-sector geographic area and correspondinggeo-bin in the potential category 2B areas the mobile station islocated.

In the embodiment being described, the northern sub-sector geographicarea and corresponding geo-bin is chosen to indicate the mobile stationlocation because the northern bin is located between base station A andbase station B where it is most likely that pilots from both basestations can be seen by the mobile station. The updated overall RFcoverage map for base station A, sector 3 is shown in FIG. 15.

With reference to FIGS. 14 and 15, the RF coverage level for thesub-sector geographic area can continue to be updated in the RF coveragemaps for each individual base station (i.e., sector antenna) byaveraging (or by taking the median value) over multiple records for acorresponding geo-bin.

With reference to FIG. 16, yet another example of an RF coverage map fora sector antenna of a base station is shown that can be used inconjunction with another exemplary embodiment of a technique forestimating the geographic location of a mobile station. In thisembodiment, the geographic location of a mobile station can be estimatedbased on RF coverage maps for various circumstances, such as droppedcall locations. Study has shown that the longer the observation period,the more accurate the results are for the corresponding RF coveragelevel. On the other hand, for some events, like dropped calls, it isvery important to know where the calls are dropped. However, undernormal circumstances, dropped calls are not experienced very often inthe wireless network. In another exemplary embodiment, a technique forestimating the location of a mobile station includes an algorithm toestimate dropped call locations for mobile stations on existing RFcoverage maps.

In this embodiment, the mobile station reports Ec/Io of base station A,sector 3 at −3 dB and Ec/Io of base station B, sector 3 at −4 dB. Thedistance between the mobile station and the serving sector antenna(i.e., base station A, sector 3) is determined to be distance d. Theprocess uses existing RF coverage maps for these sectors to identify RFcoverage levels and corresponding geo-bins that closely match thesesignal strength measurements. Moreover, the process uses the distancemeasurement to define a circle centered at base station A with a radiusdefined by distance d on which the closely matching RF coverage levelsand corresponding geo-bins are identified.

For example, the closely matching RF coverage levels for sub-sectorgeographic areas and corresponding geo-bins in a first RF coverage mapfor base station A may have Ec/Io values within a range of −3dB+/−Threshold_s, where Thresholds is a threshold for the serving sectorantenna (i.e., base station A, sector 3). For example, Threshold_s canbe set at 0.25 dB. Similarly, the closely matching RF coverage levelsfor sub-sector geographic areas and corresponding geo-bins in a secondRF coverage map for base station B may have Ec/Io values within a rangeof −4 dB+/−Threshold_n, where Threshold_n is a threshold for theneighboring sector antenna (i.e., base station B, sector 3). Forexample, Threshold_n can be set at 0.5 dB. The red dot in FIG. 16 showsthe estimated mobile station location after overlaying the sub-sectorgeographic area identified in the second RF coverage map on the first RFcoverage map to locate matching RF coverage levels from both RF coveragemaps that intersect.

With reference to FIG. 17, an exemplary embodiment of a process 1700 forestimating a geographic location of a mobile station within a coveragearea of a wireless network begins at 1702 where an instant angularposition of an individual mobile station in relation to a first basestation is calculated. The first base station including multiple sectorantennas. The instant angular position based at least in part on a firstsignal strength measurement, a second signal strength measurement, andan angular position reference that extends outward from the first basestation. The first and second signal strength measurements related incalendar time and representative of power characteristics of respectiveRF signals received by the individual mobile station from correspondingfirst and second sector antennas of the first base station.

With reference to FIGS. 17 and 18, another exemplary embodiment of aprocess 1800 for estimating a geographic location of a mobile stationwithin a coverage area of a wireless network includes the process 1700of FIG. 17 and continues at 1802 where a radial distance of theindividual mobile station from the first base station is determined. Theradial distance based at least in part on a round trip measurementassociated with elapsed time between sending an outgoing signal from thefirst base station to the individual mobile station and receiving acorresponding acknowledgement signal from the individual mobile stationat the first base station. The round trip measurement related incalendar time to the first and second signal strength measurements.

In another embodiment, the process 1800 also includes identifying aninstant geographic location of the individual mobile station in acoverage area of a wireless network formed by at least the first basestation. The instant geographic location based at least in part on anintersection of a line extending outward from the first base station atthe instant angular position with a circle having a center defined bythe first base station and a radius defined by the radial distance.

In further embodiment, the process 1800 also includes correlating theinstant geographic location of the individual mobile station with afirst sub-sector geographic area in a first RF coverage map for thefirst sector antenna based at least in part on a reference location forthe first base station in the first RF coverage map. The first RFcoverage map formed by a plurality of sub-sector geographic areas. Eachsub-sector geographic area uniquely identified and associated with acorresponding geographic location bin for the first RF coverage map forstorage of signal strength measurements from the first sector antennaassociated with the corresponding sub-sector geographic area. In thisembodiment, the process 1800 also includes sending the first signalstrength measurement to a first geographic location bin associated withthe unique identifier for the first sub-sector geographic area forstorage in conjunction with computation of a representative RF coveragelevel for populating the first sub-sector geographic area in the firstRF coverage map.

In another further embodiment, the process 1800 also includescorrelating the instant geographic location of the individual mobilestation with a second sub-sector geographic area in a second RF coveragemap for the second sector antenna based at least in part on a referencelocation for the first base station in the second RF coverage map. Thesecond RF coverage map formed by a plurality of sub-sector geographicareas. Each sub-sector geographic area uniquely identified andassociated with a corresponding geographic location bin for the secondRF coverage map for storage of signal strength measurements from thesecond sector antenna associated with the corresponding sub-sectorgeographic area. In this embodiment, the process 1800 also includessending the second signal strength measurement to a second geographiclocation bin associated with the unique identifier for the secondsub-sector geographic area for storage in conjunction with computationof a representative RF coverage level for populating the secondsub-sector geographic area in the second RF coverage map.

With reference to FIGS. 17 and 19, yet another exemplary embodiment of aprocess 1900 for estimating a geographic location of a mobile stationwithin a coverage area of a wireless network includes the process 1700of FIG. 17 and continues at 1902 where a radial distance of theindividual mobile station from a second base station serving theindividual mobile station is determined. The second base stationincluding multiple sector antennas. The radial distance based at leastin part on a round trip measurement associated with elapsed time betweensending an outgoing signal from the second base station to theindividual mobile station and receiving a corresponding acknowledgementsignal from the individual mobile station at the second base station.The round trip measurement related in calendar time to the first andsecond signal strength measurements.

In another embodiment, the process 1900 also includes identifying aninstant geographic location of the individual mobile station in acoverage area of a wireless network formed by at least the first andsecond base stations. The instant geographic location based at least inpart on an intersection of a line extending outward from the first basestation at the instant angular position with a circle having a centerdefined by the second base station and a radius defined by the radialdistance.

In a further embodiment of the process 1900, a signal strengthmeasurement report from the individual mobile station comprising thefirst and second signal strength measurements also includes a thirdsignal strength measurement. The third signal strength measurementrepresentative of the power characteristic of a third RF signal receivedby the individual mobile station from a third sector antenna of thesecond base station. In this embodiment, the process 1900 also includescorrelating the instant geographic location of the individual mobilestation with a third sub-sector geographic area in a third RF coveragemap for the third sector antenna based at least in part on a referencelocation for the second base station in the third RF coverage map. Thethird RF coverage map formed by a plurality of sub-sector geographicareas. Each sub-sector geographic area uniquely identified andassociated with a corresponding geographic location bin for the third RFcoverage map for storage of signal strength measurements from the thirdsector antenna associated with the corresponding sub-sector geographicarea. In the embodiment being described, the process 1900 also includessending the third signal strength measurement to a third geographiclocation bin associated with the unique identifier for the thirdsub-sector geographic area for storage in conjunction with computationof a representative RF coverage level for populating the thirdsub-sector geographic area in the third RF coverage map.

With reference to FIG. 20, still another exemplary embodiment of aprocess 2000 for estimating a geographic location of a mobile stationwithin a coverage area of a wireless network begins at 2002 where aradial distance of an individual mobile station from a first basestation serving the individual mobile station is calculated. The firstbase station including multiple sector antennas. The radial distancebased at least in part on a round trip measurement associated withelapsed time between sending an outgoing signal from the first basestation to the individual mobile station and receiving a correspondingacknowledgement signal from the individual mobile station at the firstbase station. Next, the process determines a signal strength report fromthe individual mobile station provided to the first base station relatedin calendar time to the round trip measurement includes a first signalstrength measurement representative of a power characteristic of a firstRF signal received by the individual mobile station from a first sectorantenna of the first base station (2004). The signal strength report notincluding other signal strength measurements for other sector antennasof the first base station.

At 2006, an instant geographic location of the individual mobile stationis identified in a coverage area of a wireless network formed by atleast the first base station. The instant geographic location based atleast in part on an intersection of a circle having a center defined bythe first base station and a radius defined by the radial distance witha first sub-sector geographic area in a first RF coverage map for thefirst sector antenna. The first RF coverage map including a firstreference location for the first base station to facilitate correlationof the circle to the first RF coverage map. The first RF coverage mapformed by a plurality of sub-sector geographic areas. The first RFcoverage map populated with representative RF coverage levels associatedwith previous signal strength measurements for the first sector antennafrom one or more mobile stations in previous signal strength reportscomprising the corresponding previous signal strength measurement and atleast one signal strength measurement from another sector antenna of thefirst base station. The first sub-sector geographic area in the first RFcoverage map is populated with a first RF coverage level representativeof lacking previous signal strength measurements.

With reference to FIGS. 20 and 21, still yet another exemplaryembodiment of a process 2100 for estimating a geographic location of amobile station within a coverage area of a wireless network includes theprocess 2000 of FIG. 20. In this embodiment of the process 2100, eachsub-sector geographic area is uniquely identified and associated with acorresponding geographic location bin for the first RF coverage map forstorage of previous signal strength measurements from the first sectorantenna associated with the corresponding sub-sector geographic area anda first geographic location bin associated with the first RF coveragemap and the first sub-sector geographic area is void of previous signalstrength measurements (2102).

In another embodiment, the process 2100 also includes identifyingmultiple sub-sector geographic areas in the first RF coverage mapintersecting the circle associated with the first base station that arepopulated with the first RF coverage level. In this embodiment, thefirst signal strength measurement is compared to representative RFcoverage levels associated with previous signal strength measurementsstored in corresponding geographic location bins for correspondingsub-sector geographic areas of the first RF coverage map neighboringeach of the multiple sub-sector geographic areas. In the embodimentbeing described, the first sub-sector geographic area is selected fromthe multiple sub-sector geographic areas based at least in part on theneighboring RF coverage level for the first sub-sector geographic areabeing associated with previous signal strength measurements that arecloser to the first signal strength measurement than previous signalstrength measurements associated with neighboring RF coverage levels forother sub-sector geographic areas of the multiple sub-sector geographicareas.

In yet another embodiment, the process 2100 also includes sending thefirst signal strength measurement to a first geographic location binassociated with the unique identifier for the first sub-sectorgeographic area for storage in conjunction with computation of arepresentative RF coverage level for populating the first sub-sectorgeographic area in a second RF coverage map for the first sectorantenna. The second RF coverage map formed by a plurality of sub-sectorgeographic areas. The second RF coverage map populated withrepresentative RF coverage levels associated with previous signalstrength measurements for the first sector antenna from one or moremobile stations in previous signal strength reports.

With reference to FIGS. 20 and 22, another exemplary embodiment of aprocess 2200 for estimating a geographic location of a mobile stationwithin a coverage area of a wireless network includes the process 2000of FIG. 20 and continues at 2202 with determining the signal strengthreport from the individual mobile station provided to the first basestation includes a second signal strength measurement representative ofthe power characteristic of a second RF signal received by theindividual mobile station from a second sector antenna of a second basestation. The second base station including multiple sector antennas. Inthis embodiment of the process 2200, the first RF coverage map includesa second reference location for the second base station.

In another embodiment, the process 2200 also includes identifyingmultiple sub-sector geographic areas in the first RF coverage mapintersecting the circle associated with the first base station that arepopulated with the first RF coverage level. In this embodiment,geographic locations of the multiple sub-sector geographic areas in thefirst RF coverage map are compared to a fixed location for the secondbase station in relation to the first RF coverage map. In the embodimentbeing described, the first sub-sector geographic area is selected fromthe multiple sub-sector geographic areas based at least in part on thegeographic location for the first sub-sector geographic area beingcloser to the fixed location for the second base station than thegeographic locations for other sub-sector geographic areas of themultiple sub-sector geographic areas.

In yet another embodiment, the process 2200 also includes correlatingthe instant geographic location of the individual mobile station with asecond sub-sector geographic area in a second RF coverage map for thesecond sector antenna based at least in part on a second referencelocation for the first base station in the second RF coverage map. Thesecond RF coverage map formed by a plurality of sub-sector geographicareas. Each sub-sector geographic area uniquely identified andassociated with a corresponding geographic location bin for the secondRF coverage map for storage of signal strength measurements from thesecond sector antenna associated with the corresponding sub-sectorgeographic area. In this embodiment, the process 2200 also includessending the second signal strength measurement to a second geographiclocation bin associated with the unique identifier for the secondsub-sector geographic area for storage in conjunction with computationof a representative RF coverage level for populating the secondsub-sector geographic area in the second RF coverage map for the secondsector antenna.

With reference to FIG. 23, yet another exemplary embodiment of a process2300 for estimating a geographic location of a mobile station within acoverage area of a wireless network begins at 2302 where a radialdistance of an individual mobile station from a first base stationserving the individual mobile station is calculated in response todetection of a dropped call for the mobile station. The first basestation including multiple sector antennas. The radial distance based atleast in part on a round trip measurement preceding detection of thedropped call and in proximate time relation to detection of the droppedcall. The round trip measurement associated with elapsed time betweensending an outgoing signal from the first base station to the individualmobile station and receiving a corresponding acknowledgement signal fromthe individual mobile station at the first base station. Next, theprocess determines a signal strength report from the individual mobilestation provided to the first base station preceding detection of thedropped call, in proximate time relation to detection of the droppedcall, and related in calendar time to the round trip measurementincludes a first signal strength measurement representative of a powercharacteristic of a first RF signal received by the individual mobilestation from a first sector antenna of the first base station (2304).

At 2306, an instant geographic location of the individual mobile stationis identified in a coverage area of a wireless network formed by atleast the first base station. Identification of the instant geographiclocation is based at least in part on an intersection of a circle havinga center defined by the first base station and a radius defined by theradial distance with a first sub-sector geographic area in a first RFcoverage map for the first sector antenna. The first RF coverage mapincluding a first reference location for the first base station tofacilitate correlation of the circle to the first RF coverage map. Thefirst RF coverage map formed by a plurality of sub-sector geographicareas. The first RF coverage map populated with representative RFcoverage levels associated with previous signal strength measurementsfor the first sector antenna from one or more mobile stations inprevious signal strength reports. The first sub-sector geographic areain the first RF coverage map is populated with an RF coverage levelrepresentative of a first signal strength value within a firstpredetermined threshold of the first signal strength measurement.

In another embodiment, the process 2300 also includes identifyingmultiple sub-sector geographic areas in the first RF coverage mapintersecting the circle associated with the first base station that arepopulated with RF coverage levels representative of first signalstrength values within the predetermined threshold of the first signalstrength measurement. In this embodiment, the process determines thesignal strength report from the individual mobile station provided tothe first base station includes a second signal strength measurementrepresentative of the power characteristic of a second RF signalreceived by the individual mobile station from a second sector antennaof a second base station. The second base station including multiplesector antennas.

In a further embodiment, the process 2300 also includes comparinggeographic locations of the multiple sub-sector geographic areas in thefirst RF coverage map to a fixed location for the second base station inrelation to the first RF coverage map. In this embodiment, the firstsub-sector geographic area is selected from the multiple sub-sectorgeographic areas based at least in part on the geographic location forthe first sub-sector geographic area being closer to the fixed locationfor the second base station than the geographic locations for othersub-sector geographic areas of the multiple sub-sector geographic areas.

In another further embodiment, the process 2300 also includescorrelating the circle associated with the first base station with asecond RF coverage map for the second sector antenna based at least inpart on the second RF coverage map including the first referencelocation for the first base station and a second reference location forthe second base station. The second RF coverage map formed by aplurality of sub-sector geographic areas. The second RF coverage mappopulated with representative RF coverage levels associated withprevious signal strength measurements for the second sector antenna fromone or more mobile stations in previous signal strength reports. In thisembodiment, the process 2300 also includes identifying a secondsub-sector geographic area in the second RF coverage map based at leastin part on the circle associated with the first base stationintersecting at least one sub-sector geographic area in the second RFcoverage map populated with an RF coverage level representative of asecond signal strength value within a second predetermined threshold ofthe second signal strength measurement. In the embodiment beingdescribed, the second sub-sector geographic area in the second RFcoverage map is correlated with the first RF coverage map based at leastin part on the first and second RF coverage maps including the first andsecond reference locations for the first and second base stations toidentify the first sub-sector geographic area.

In yet another further embodiment, the process 2300 also includesidentifying multiple prospective geographic locations for the mobilestation in a second RF coverage map for the second sector antenna. Thesecond RF coverage map including the first reference location for thefirst base station and a second reference location for the second basestation. The second RF coverage map formed by a plurality of sub-sectorgeographic areas. The second RF coverage map populated withrepresentative RF coverage levels associated with previous signalstrength measurements for the second sector antenna from one or moremobile stations in previous signal strength reports. The multipleprospective geographic locations based at least in part on thecorresponding sub-sector geographic areas in the second RF coverage mapbeing populated with an RF coverage level representative of a secondsignal strength value within a second predetermined threshold of thesecond signal strength measurement. In this embodiment, the process 2300also includes correlating the multiple prospective geographic locationsfor the mobile station in the second RF coverage map with the first RFcoverage map for the first sector antenna based at least in part on thefirst and second RF coverage maps including the first reference locationfor the first base station. In the embodiment being described,identification of the instant geographic location is based at least inpart on at least one of the multiple prospective geographic locationsintersecting the circle associated with the first base station in thefirst RF coverage map.

With reference to FIG. 2, in one embodiment, the technique forestimating the geographic location of the mobile station uses a roundtrip measurement (e.g., RTD measurement) from a serving base station(i.e., serving cell) to estimate the distance (d) of the mobile stationfrom the serving base station. Then, signal strength measurements fromserving and/or neighboring sectors of the serving base station toestimate an azimuth position (φ) of the mobile station in relation to anangular position reference extending outward from the serving basestation. Combining the sector coverage areas of the same base stationforms a corresponding cellular coverage area for the base station. Theindividual sector coverage areas may also be referred to as cells inrelation to corresponding sector antennas. If so, the correspondingcells for sector antennas associated with the same base station arestill usually labeled as sectors (e.g., α, β, γ sectors or sectors 1, 2,3). Normally, the sector antennas associated with the same base stationare mounted on the same cell tower (or building). Hence, the radio wavetravel from these sector antennas to a given mobile station antenna willexperience highly correlated losses (including path loss and shadowfading). The algorithm described herein uses these RF characteristics(i.e., highly correlated losses) to estimate an azimuth position of themobile station in relation to the serving based station based on thedifference of signal strength measurements from multiple sector antennasof the serving base station.

In one embodiment, the algorithm for estimating a geographic location ofa mobile station within a coverage area of a wireless network beginswith estimating a distance (d) of the mobile station from the servingbase station based on a round trip measurement, such as RTD. Next, theazimuth position (φ) of the mobile station in relation to the servingbase station is estimated based on signal strength measurements by themobile station from multiple sector antennas of the serving base stationthat are reported back by the mobile station to the serving base stationvia the serving sector antenna. Combining the distance (d) and azimuthposition (φ) forms a geographic location of the mobile station inrelation to the serving base station with respect to vector representedby a displacement (i.e., distance (d)) and an angular position (i.e.,azimuth position (φ)). This polar coordinate-type of geographic notationcan be converted to various other forms of geographic notation,including a latitude/longitude notation, an address notation, or ageo-bin tile grid notation associated with the coverage area for thewireless network. For example, the geo-bin tile grid notation may use 50meter by 50 meter tiles to represent the coverage area for a sectorantenna, base station, cluster of base stations, or the overall wirelessnetwork. In other embodiments, any suitable tile size may be used toprovide a higher or lower resolution of the coverage area.

The approximation algorithm for estimating the geographic location of amobile station may be based on certain considerations regarding themobile received power (Pr) (i.e., signal strength measurements) frommultiple sector antennas where the sector antennas are located in closeproximity to each other, such as mounted on the same cell tower or onthe same physical structure at relatively the same elevation. Forexample, the mobile received power (Pr) is received by the mobilestation from multiple sector antennas of the serving base station. Themobile station measures the signal strength of the mobile received power(Pr) signals and may report back the corresponding signal strengthmeasurements in dBm.

Mobile received power (Pr) may be represented by the following equation:Pr(d,φ,Θ)=Pt−PL(d)−X+Gt(d,φ,Θ)+Gr  (1),where d is a distance between the serving base station and the mobilestation in kilometers (km), φ is an azimuth position of the mobilestation in relation to an angular position reference extending outwardfrom the serving base station, Θ is an azimuth position at which thetransmit portion of the corresponding sector antenna is oriented inrelation to the angular reference position, Pt is a transmit power forthe corresponding sector antenna in dBm, and PL(d) is an average pathloss in dB for the corresponding sector antenna. The azimuth position Θof the sector antenna is known and corresponds to its actualinstallation. Likewise, the transmit power Pt for the sector antenna isknown at the serving base station based on known characteristics of thesector antenna or actual measurements by the base station.

The average path loss PL(d) may be represented by the followingequation:PL(d)=K1+K2*log 10(d)  (2),where K1 and K2 are propagation parameters such that K1 is function ofmorphology, frequency, cell antenna height, and mobile antenna heightand K2 is function of cell antenna height.

With reference again to equation (1), X is a zero-mean Gaussiandistributed random variable (in dB) with standard deviation σapproximately equal to N(0, σ). (in dB). X may be referred to as theshadowing fading effect. Gt(d, φ, Θ) is the transmit antenna gain at thesector antenna in dB. Gr is receive antenna gain at the mobile stationin dB.

With reference to FIG. 3, Gt(d, φ, Θ) reflects that Gt is a function ofmobile distance (d) and an angle between the azimuth position (φ) of themobile station and the azimuth position (Θ) of the corresponding sectorantenna. Note, the distance (d), in combination with the sector antennaheight, is used to estimate an antenna tile and an antenna downtile. Theazimuth position (φ) of the mobile station and the azimuth position (Θ)of the corresponding sector antenna are used to determine a horizontalgain portion of Gt, where the look angle is φ−Θ. The distance (d) andthe height (i.e., elevation) of the corresponding sector antenna areused to determine a vertical gain component of Gt.

The signal strength measurements for mobile received power Pr may bereported as received signal reference power (RSRP) measurements,reference signal received quality (RSRQ) measurements, or Ec/Iomeasurements. RSRQ is the ratio of received signal reference power tototal received power. Ec/Io is the ratio in dB between the pilot energyaccumulated over one PN chip period (“Ec”) to the total power spectraldensity in the received bandwidth (“Io”).

Mobile received power Pr1 and Pr2 from two sector antennas of theserving base station in dBm may be represented by the followingequations:Pr1(d,φ,Θ1)=Pt1−PL(d)−X+Gt1(d,φ,Θ1)+Gr  (3),Pr2(d,φ,Θ2)=Pt2−PL(d)−X+Gt2(d,φ,Θ2)+Gr+ε  (4).

The path loss and shadowing fading effect from different sector antennasof the same base station can be assumed to be equal where the sectorantennas are mounted on the same cell tower or building. The closeproximity of the sector antennas results in high correlation of betweenthese components of the mobile received power Pr1 and Pr2. For example,the differences of shadow fading are expected to be very small and arecounted by ε in equation (4). As mentioned above, d, Θ1 and Θ2 are knownvalues.

Based on the foregoing, an estimate of the azimuth position (φ) of themobile station may be based on the difference of mobile received powerfrom the two sector antennas (Pr1−Pr2) in dB. For example, (Pr1−Pr2) canbe (RSRP1−RSRP2) or (RSRQ1−RSRQ2) in an LTE network. Similarly,(Pr1−Pr2) can be (Ec/Io) 1−(Ec/Io) 2 in a CDMA network. Even though themobile received power Pr1 and Pr2 are expressed in absolute receivedpower format (i.e., dBm), the estimation of mobile location does notrequire the knowledge of absolute received power information. RSRQ forLTE and pilot Ec/Io for CDMA can be used in the same manner as mentionedabove.

Based on the foregoing, the difference between the mobile received powerPr1 and Pr2 can be represented by the following equation:(Pr1−Pr2)=(Gt1(φ)−Gt2(φ))+(Pt1−Pt2)  (5),where φ can be substituted with a potential azimuth position φm for themobile station in the range of 0 to 360 degrees. The potential azimuthposition φm that results in the closest match between the right and leftsides of equation (5) can be used as estimated azimuth position of themobile station.

Based on the foregoing, the azimuth position of the mobile station canbe represented by the following equation:F(φ)=|(Gt1(φ)−Gt2(φ))+(Pt1−Pt2)−(Pr1−Pr2)|  (6),where φ can be substituted with a potential azimuth position φm for themobile station in the range of 0 to 360 degrees. The potential azimuthposition φm that minimizes F(φm) can be used as estimated azimuthposition of the mobile station.

This process can also be expressed in the following equation:min|(Gt1(φ)−Gt2(φ))+(Pt1−Pt2)−(Pr1−Pr2)|  (7).

Notably, the value selected for the initial potential azimuth positionφm in equations (5) through (7) can be based at least in part on theknowledge of the orientation and azimuth position of the serving sectorantenna. Subsequent values selected for the potential azimuth positionφm can be based on whether the subsequent result is approaching orreceding from the desired result. Various techniques can also be used toselect subsequent values for the potential azimuth position φm based onthe magnitude of the difference between the subsequent result and thedesired result as well as the change in the difference betweenconsecutive subsequent results and the desired result.

With reference to FIG. 11, a bird's eye view of a coverage area of anexemplary base station A in a wireless network shows an estimatedgeographic location for a mobile station (UE) resulting from the processdisclosed herein. A geographic location for the mobile station (UE)based on GPS location is also shown for comparison. The X and Y axes forthe coverage area reflect distance in meters from the base station A.Notably, the estimated geographic location is close to the GPS location.

The base station A includes a first sector antenna oriented at 27degrees from north (i.e., an angular position reference representing0/360 degrees) and a second sector antenna oriented at 267 degrees. Themobile station reported signal strength measurements from the first andsecond sector antennas at −11 dB and −13 dB, respectively. The angularposition of the mobile station was estimated at 330.6 degrees using theprocess disclosed herein. The measurements used to estimate thegeographic location of the mobile station were retrieved from per callmeasurement data (PCMD) for an active call associated with the mobilestation. For example, the PCMD data may be stored by a wireless serviceprovider during network operations for billing purposes. The processdisclosed herein may use signal strength measurements and round tripmeasurements captured and retained during network operations via anysuitable techniques without requiring additional network overhead forcollection of data to perform the estimate of the geographic location ofthe mobile station.

With reference to FIG. 12, various data and calculations associated withthe process for estimating the geographic location of a mobile stationis provided in a set of graphs. The upper left graph shows an azimuthgain parameter characteristic for a first sector antenna of a servingbase station. The first sector antenna is oriented at 27 degrees fromnorth (i.e., an angular position reference representing 0/360 degrees).The middle left graph shows an azimuth gain parameter characteristic fora second sector antenna of a serving base station. The second sectorantenna is oriented at 267 degrees from north. The azimuth gainparameter characteristics may be manufacturer's specifications of powermeasurements from the sector antennas from relatively close (e.g., 10meters) to the base station where little or no path loss is experienced.As shown, the first and second sector antennas have the same azimuthgain characteristic merely shifted by the orientation of the antennas.In other base station arrangements, the sector antennas may havedifferent azimuth gain characteristics.

The upper right graph shows an elevation gain parameter characteristicfor the first sector antenna. The first sector antenna is oriented at 2degrees down from horizontal (i.e., an elevation position referencerepresenting 0/360 degrees). The middle right graph shows an elevationgain parameter characteristic for the second sector antenna. The secondsector antenna is also oriented at 2 degrees down from horizontal. Theelevation gain parameter characteristics may be manufacturer'sspecifications of power measurements from the sector antennas fromrelatively close (e.g., 10 meters) to the base station where little orno path loss is experienced. As shown, the first and second sectorantennas have the same elevation gain characteristic. In other basestation arrangements, the sector antennas may have different elevationgain characteristics. Also, the sector antennas may be oriented atdifferent angles from the horizontal in other base station arrangements.

The lower left graph is a composite graph showing the difference betweengains for the first and second sector antennas. The composite graphtakes the azimuth and elevation gain characteristics into account toform a composite delta gain characteristic. The composite graph reflectsdifferences in relation to varying azimuth position that follows theazimuth gain characteristics and a relatively steady state componentfrom the elevation gain characteristics because the elevation tilt ofthe antennas is not changing. The following equation is used to populatethe composite graph:(Gt1(φ)_(az) +Gt1_(el) −Gt1_(max))−(Gt2(φ)_(az) +Gt2_(el)−Gt2_(max))  (8),where Gt1(φ)_(az) is the azimuth gain for the first sector antenna for agiven azimuth angle in relation to the angular position reference, Gt1_(el) is the elevation gain for the first antenna associated with theelevation tilt, and Gt1 _(max) is the maximum gain for the first sectorantenna. Similarly, Gt2(φ)_(az) is the azimuth gain for the secondsector antenna for a given azimuth angle in relation to the angularposition reference, Gt2 _(el) is the elevation gain for the secondantenna associated with the elevation tilt, and Gt2 _(max) is themaximum gain for the second sector antenna.

The lower right graph shows a function of the angular position of themobile station in relation to the delta antenna gain component, a deltatransmit parameter component, and a delta signal strength measurementcomponent as defined above in equation (7).

With reference to FIG. 4, an exemplary embodiment of a process 400 forestimating a geographic location of a mobile station within a coveragearea of a wireless network begins at 402 where a radial distance of amobile station from a base station serving the mobile station isdetermined. The base station includes multiple sector antennas. Theradial distance is based at least in part on a round trip measurementassociated with elapsed time between sending an outgoing signal from thebase station to the mobile station and receiving a correspondingacknowledgement signal from the mobile station at the base station. At404, a current angular position of the mobile station in relation to theradial distance from the serving base station is calculated. The currentangular position is based at least in part on a first signal strengthmeasurement, a second signal strength measurement, and an angularposition reference that extends outward from the serving base station.The first and second signal strength measurements representative ofpower characteristics of respective RF signals received by the mobilestation from corresponding first and second sector antennas of theserving base station.

With reference to FIGS. 4 and 5, another exemplary embodiment of aprocess 500 for estimating a geographic location of a mobile stationwithin a coverage area of a wireless network includes the process 400 ofFIG. 4 and continues at 502 where a current geographic location of themobile station in a coverage area of the wireless network is identifiedin a geographic notation. The geographic notation is based at least inpart on combining the radial distance and current angular position ofthe mobile station relative to the serving base station. In oneembodiment, the radial distance and current angular position reflect apolar coordinate-type of geographic notation in reference to the servingbase station. In other embodiments, the radial distance and currentangular position can be converted into various types of geographicnotation, such as a latitude/longitude notation, an address notation, ora geo-bin tile grid notation associated with the coverage area for thewireless network.

In another embodiment, the process 500 also includes sending the currentgeographic location of the mobile station in the geographic notation toa geo-location storage node associated with the wireless network. In afurther embodiment, the determining, calculating, identifying, andsending are performed by the serving base station.

In yet another embodiment, the process 500 also includes receiving theround trip measurement, first signal strength measurement, and secondsignal strength measurement from the serving base station via thewireless network at a geo-location service node associated with thewireless network. In this embodiment, the current geographic location ofthe mobile station is sent in the geographic notation to a geo-locationstorage device associated with the geo-location service node. In theembodiment being described, the receiving, determining, calculating,identifying, and sending are performed by the geo-location service node.

In still another embodiment, the process 500 also includes receiving theround trip measurement, first signal strength measurement, and secondsignal strength measurement from the serving base station via thewireless network at a network management node associated with thewireless network. In this embodiment, the round trip measurement, firstsignal strength measurement, and second signal strength measurement arestored at a measurements storage device associated with the networkmanagement node. In the embodiment being described, the round tripmeasurement, first signal strength measurement, and second signalstrength measurement are retrieved from the measurements storage devicein conjunction with the determining and calculating. In this embodiment,the process 500 also includes sending the current geographic location ofthe mobile station in the geographic notation to a geo-location storagedevice associated with the network management node. The receiving,storing, retrieving, determining, calculating, identifying, and sendingare performed by the network management node in the embodiment beingdescribed.

With reference again to FIG. 4, in another embodiment of the process400, the round trip, first signal strength, and second signal strengthmeasurements are related in calendar time. In a further embodiment, theradial distance and current angular position of the mobile stationrelative to the serving base station are indicative of a currentgeographic location of the mobile station in a coverage area of thewireless network in relation to the calendar time associated with theround trip, first signal strength, and second signal strengthmeasurements.

In yet another embodiment of the process 400, the first sector antennais serving the mobile station and referred to as a serving sectorantenna and the second sector antenna is disposed near the first sectorantenna and referred to as a neighboring sector antenna. In stillanother embodiment of the process 400, the round trip measurement ismeasured by the serving base station. In a further embodiment, the roundtrip measurement includes a RTD time measurement. In still yet anotherembodiment of the process 400, the first and second signal strengthmeasurements are measured by the mobile station. In a furtherembodiment, the first and second signal strength measurements includeRSRP measurements, RSRQ measurements, or Ec/Io measurements.

In another embodiment of the process 400, the calculating in 404 mayinclude retrieving first and second transmit parameter values from astorage device associated with the wireless network. The first andsecond transmit parameter values representative of power characteristicsof respective communication signals to be transmitted by thecorresponding first and second sector antennas. In this embodiment, thecalculating in 404 may also include determining a difference between thefirst and second transmit parameter values to obtain a first angularposition component.

In a further embodiment of the process 400, the calculating in 404 mayalso include retrieving the first and second signal strengthmeasurements from the storage device. In this embodiment, thecalculating in 404 may also include determining a difference between thefirst and second signal strength measurements to obtain a second angularposition component.

In a yet further embodiment of the process 400, the calculating in 404may also include retrieving a first antenna elevation gain parametervalue, a first antenna maximum gain parameter value, and a first antennaazimuth gain parameter characteristic from the storage device. The firstantenna azimuth gain parameter characteristic relating first antennaazimuth gain parameter values to variable azimuth positions with respectto the angular position reference. The variable azimuth positionsrepresentative of prospective azimuth positions of the mobile station inrelation to the angular position reference. The first antenna azimuthgain parameter characteristic based at least in part on a first antennaposition value representative of a first azimuth position at which thefirst sector antenna is oriented in relation to the angular positionreference. In this embodiment, a second antenna elevation gain parametervalue, a second antenna maximum gain parameter value, and a secondantenna azimuth gain parameter characteristic are also retrieved fromthe storage device. The second antenna azimuth gain parametercharacteristic relating second antenna azimuth gain parameter values tothe variable azimuth positions. The second antenna azimuth gainparameter characteristic based at least in part on a second antennaposition value representative of a second azimuth position at which thesecond sector antenna is oriented in relation to the angular positionreference.

In the embodiment being described, an angular value (e.g., not exceeding360) may be selected for the variable azimuth position. The first andsecond antenna azimuth gain parameter characteristics may be used toidentify the corresponding first and second antenna azimuth gainparameter values for the variable azimuth position associated with theselected angular value. In this embodiment, the calculating in 404 maycontinue by determining a difference between first and second transmitantenna gains for the selected angular value. The difference may bedetermined by adding the first antenna azimuth gain parameter value forthe selected angular value to the first antenna elevation gain parametervalue and subtracting the first antenna maximum gain parameter value toobtain the first transmit antenna gain, adding the second antennaazimuth gain parameter value for the selected angular value to thesecond antenna elevation gain parameter value and subtracting the secondantenna maximum gain parameter value to obtain the second transmitantenna gain, and subtracting the second transmit antenna gain from thefirst transmit antenna gain to obtain a third angular positioncomponent.

The angular value selected for the initial variable azimuth position canbe based at least in part on knowledge of which sector antenna isserving the mobile station and the orientation and azimuth position ofthe serving sector antenna. Subsequent values selected for the variableazimuth position can be based on whether the subsequent result isapproaching or receding from the desired result. Various techniques canalso be used to select subsequent values for the variable azimuthposition based on the magnitude of the difference between the subsequentresult and the desired result as well as the change in the differencebetween consecutive subsequent results and the desired result.

For example, in a further embodiment of the process 400, the angularvalue initially selected for the variable azimuth position may bebetween the first and second antenna position values. In thisembodiment, the initial angular value may be representative of amid-point between the first and second antenna position values. In otherwords, if the first antenna is oriented to 120 degrees in relation tothe angular reference position, a second antenna may be oriented to 240degrees, and 180 may be selected as the initial angular value for thevariable azimuth position because it is at a midpoint between the firstand second sector antennas. The selection of other angular values forthe variable azimuth position can take into account whether the resultsare getting better or worse to select angular values to obtain betterresults. The iterative selection of angular values can be incremental orbased on a factor of the difference between the obtained result and thedesired result.

In still another further embodiment of the process 400, the calculatingin 404 also includes adding the first and third angular positioncomponents and subtracting the second angular position component to forman arithmetic result. In the embodiment being described, the arithmeticresult is converted to an absolute value. In this embodiment, if theabsolute value is within a predetermined threshold of a desired value(e.g., zero), the process 400 continues by identifying the angular valuesubstituted for the variable azimuth position as the current angularposition for the mobile station. Otherwise, the process 400 repeats theselecting with a different angular value, repeats the determining of thedifference between the first and second transmit gains to obtain a newvalue for the third angular position component, repeats the adding andsubtracting to form the arithmetic result and the determining of theabsolute value, and continues the repeating until the absolute value iswithin the predetermined threshold of the desired value.

In still yet another further embodiment of the process 400, thecalculating in 404 also includes adding the first and third angularposition components and subtracting the second angular positioncomponent to form an arithmetic result. In this embodiment, thearithmetic result is converted to an absolute value. In the embodimentbeing described, the process 400 repeats the selecting with a differentangular value, repeats the determining of the difference between thefirst and second transmit gains to obtain a new value for the thirdangular position component, repeats the adding and subtracting to formthe arithmetic result and the determining of the absolute value, andcontinues the repeating until the absolute value is minimized. In thisembodiment, the process 400 continues by identifying the correspondingangular value substituted for the variable azimuth position for whichthe absolute value is minimized as the current angular position for themobile station.

In another further embodiment of the process 400, the calculating in 404includes summing the first and third angular position components to forman arithmetic result and comparing the arithmetic result to the secondangular position component. In this embodiment, if the arithmetic resultis within a predetermined range of the second angular positioncomponent, the process 400 continues by identifying the angular valuesubstituted for the variable azimuth position as the current angularposition for the mobile station. Otherwise, the process 400 repeats theselecting with a different angular value, repeats the determining of thedifference between the first and second transmit gains to obtain a newvalue for the third angular position component, repeats the summing ofthe first and third angular position components to form the arithmeticresult and the comparing of the arithmetic result to the second angularposition component, and continues the repeating until the arithmeticresult is within the predetermined range of the second angular positioncomponent.

With reference to FIG. 6, an exemplary embodiment of an apparatus forestimating a geographic location of a mobile station 600 within acoverage area of a wireless network 602 includes a distance module 604and an angular position module 606. The distance module 604 determines aradial distance of the mobile station 600 from a base station 608serving the mobile station 600. The base station 608 includes multiplesector antennas (e.g., 610, 612, 614). The radial distance is based atleast in part on a round trip measurement associated with elapsed timebetween sending an outgoing signal from the base station 608 to themobile station 600 and receiving a corresponding acknowledgement signalfrom the mobile station 600 at the base station 608. The angularposition module 606 is in operative communication with the distancemodule 604 and calculates a current angular position of the mobilestation 600 in relation to the radial distance from the serving basestation 608. The current angular position is based at least in part on afirst signal strength measurement, a second signal strength measurement,and an angular position reference that extends outward from the servingbase station 608. The first and second signal strength measurementsrepresentative of power characteristics of respective RF signalsreceived by the mobile station 600 from corresponding first and secondsector antennas 610, 612 of the serving base station 608. The currentangular position may also be based on additional signal strengthmeasurements from other sector antennas 614 (e.g., sector antenna N).

In this embodiment, the apparatus may also include a location module 616in operative communication with the distance module 604 and angularposition module 606 for identifying a current geographic location of themobile station 600 in a coverage area of the wireless network 602 in ageographic notation based at least in part on combining the radialdistance and current angular position of the mobile station 600 relativeto the serving base station 608. In one embodiment, the radial distanceand current angular position reflect a polar coordinate-type ofgeographic notation in reference to the serving base station. In otherembodiments, the radial distance and current angular position can beconverted into various types of geographic notation, such as alatitude/longitude notation, an address notation, or a geo-bin tile gridnotation associated with the coverage area for the wireless network.

In the embodiment being described, the apparatus may also include anoutput module 618 in operative communication with the location module616 for sending the current geographic location of the mobile station600 in the geographic notation to a geo-location storage node 620associated with the wireless network 602. The geo-location storage node620 may be internal or external to the wireless network 602. In thisembodiment, the apparatus may include the serving base station 608. Inthis embodiment, the serving base station 608 may include the distancemodule 604, angular position module 606, location module 616, and outputmodule 618.

With reference to FIG. 7, an exemplary embodiment of an apparatus forestimating a geographic location of a mobile station 700 within acoverage area of a wireless network 702 includes a distance module 704and an angular position module 706. The distance module 704 determines aradial distance of the mobile station 700 from a base station 708serving the mobile station 700. The radial distance is based at least inpart on a round trip measurement associated with elapsed time betweensending an outgoing signal from the base station 708 to the mobilestation 700 and receiving a corresponding acknowledgement signal fromthe mobile station 700 at the base station 708. The angular positionmodule 706 is in operative communication with the distance module 704and calculates a current angular position of the mobile station 700 inrelation to the radial distance from the serving base station 708. Thecurrent angular position is based at least in part on a first signalstrength measurement, a second signal strength measurement, and anangular position reference that extends outward from the serving basestation 708. The first and second signal strength measurementsrepresentative of power characteristics of respective RF signalsreceived by the mobile station 700 from corresponding first and secondsector antennas 710, 712 of the serving base station 708. The currentangular position may also be based on additional signal strengthmeasurements from other sector antennas 714 (e.g., sector antenna N).

In this embodiment, the apparatus may also include a location module 716in operative communication with the distance module 704 and angularposition module 706 for identifying a current geographic location of themobile station 700 in a coverage area of the wireless network 702 in ageographic notation based at least in part on combining the radialdistance and current angular position of the mobile station 700 relativeto the serving base station 708.

In the embodiment being described, the apparatus may include ageo-location service node 722 associated with the wireless network 702and in operative communication with the serving base station 708. Inthis embodiment, the geo-location service node 722 may include thedistance module 704, angular position module 706, and location module716.

The geo-location service node 722 may also include an input module 724and an output module 718. The input module 724 in operativecommunication with the distance module 704 and angular position module706 for receiving the round trip measurement, first signal strengthmeasurement, and second signal strength measurement from the servingbase station 708 via the wireless network 702. The output module 718 inoperative communication with the location module 716 for sending thecurrent geographic location of the mobile station 700 in the geographicnotation to a geo-location storage device 726 associated with thegeo-location service node 722. The geo-location storage device 726 maybe internal or external to the geo-location service node 722. If thegeo-location storage device 726 is external to the geo-location servicenode 722, the geo-location storage device 726 may be internal orexternal to the wireless network 702.

With reference to FIG. 8, an exemplary embodiment of an apparatus forestimating a geographic location of a mobile station 800 within acoverage area of a wireless network 802 includes a distance module 804and an angular position module 806. The distance module 804 determines aradial distance of the mobile station 800 from a base station 808serving the mobile station 800. The radial distance is based at least inpart on a round trip measurement associated with elapsed time betweensending an outgoing signal from the base station 808 to the mobilestation 800 and receiving a corresponding acknowledgement signal fromthe mobile station 800 at the base station 808. The angular positionmodule 806 is in operative communication with the distance module 804and calculates a current angular position of the mobile station 800 inrelation to the radial distance from the serving base station 808. Thecurrent angular position is based at least in part on a first signalstrength measurement, a second signal strength measurement, and anangular position reference that extends outward from the serving basestation 808. The first and second signal strength measurementsrepresentative of power characteristics of respective RF signalsreceived by the mobile station 800 from corresponding first and secondsector antennas 810, 812 of the serving base station 808. The currentangular position may also be based on additional signal strengthmeasurements from other sector antennas 814 (e.g., sector antenna N).

In this embodiment, the apparatus may also include a location module 816in operative communication with the distance module 804 and angularposition module 806 for identifying a current geographic location of themobile station 800 in a coverage area of the wireless network 802 in ageographic notation based at least in part on combining the radialdistance and current angular position of the mobile station 800 relativeto the serving base station 808.

In the embodiment being described, the apparatus may include a networkmanagement node 828 associated with the wireless network 802 and inoperative communication with the serving base station 808. In thisembodiment, the network management node 828 may include the distancemodule 804, angular position module 806, and location module 816.

The network management node 828 may also include an input module 824, ameasurements storage device 830, and an output module 818. The inputmodule 824 for receiving the round trip measurement, first signalstrength measurement, and second signal strength measurement from theserving base station 808 via the wireless network 802. The measurementsstorage device 830 in operative communication with the input module 824,distance module 804, and angular position module 806 for storing theround trip measurement, first signal strength measurement, and secondsignal strength measurement. In this embodiment, the distance module 804retrieves the round trip measurement from the measurements storagedevice 830 in conjunction with determining the radial distance.Similarly, the angular position module 806 retrieves the first andsecond signal strength measurements from the measurements storage device830 in conjunction with calculating the current angular position. Theoutput module 818 in operative communication with the location module816 for sending the current geographic location of the mobile station800 in the geographic notation to the geo-location storage device 826.The geo-location storage device 826 may be internal or external to thenetwork management node 828. If the geo-location storage device 826 isexternal to the network management node 828, the geo-location storagedevice 826 may be internal or external to the wireless network 802.

With reference to FIG. 9, an exemplary embodiment of an angular positionmodule 906 associated with the apparatus of FIGS. 6-8 may include asource data communication sub-module 932 and a first angular componentsub-module 938. The source data communication sub-module 932 forretrieving first and second transmit parameter values from a storagedevice 936 associated with the wireless network. The first and secondtransmit parameter values representative of power characteristics ofrespective communication signals to be transmitted by the correspondingfirst and second sector antennas (e.g., 610, 612). In this embodiment,the first angular component sub-module 938 is in operative communicationwith the source data communication module 932 for determining adifference between the first and second transmit parameter values toobtain a first angular position component.

In a further embodiment of the angular position module 906, the sourcedata communication module may retrieve the first and second signalstrength measurements from the storage device 936. In this embodiment,the angular position module 906 may also include a second angularcomponent module 940 in operative communication with the source datacommunication module 932 for determining a difference between the firstand second signal strength measurements to obtain a second angularposition component.

In a yet further embodiment of the angular position module 906, thesource data communication sub-module 932 may also retrieve a firstantenna elevation gain parameter value, a first antenna maximum gainparameter value, and a first antenna azimuth gain parametercharacteristic from the storage device 936. The first antenna azimuthgain parameter characteristic relating first antenna azimuth gainparameter values to variable azimuth positions with respect to theangular position reference. The variable azimuth positionsrepresentative of prospective azimuth positions of the mobile station900 in relation to the angular position reference. The first antennaazimuth gain parameter characteristic based at least in part on a firstantenna position value representative of a first azimuth position atwhich the first sector antenna 910 is oriented in relation to theangular position reference.

In this embodiment, the source data communication sub-module 932 mayalso retrieve a second antenna elevation gain parameter value, a secondantenna maximum gain parameter value, and a second antenna azimuth gainparameter characteristic from the storage device 936. The second antennaazimuth gain parameter characteristic relating second antenna azimuthgain parameter values to the variable azimuth positions. The secondantenna azimuth gain parameter characteristic based at least in part ona second antenna position value representative of a second azimuthposition at which the second sector antenna 912 is oriented in relationto the angular position reference.

In the embodiment being described, the angular position module 906 mayalso include a third angular component sub-module 934 in operativecommunication with the source data communication sub-module 932. Thethird angular component sub-module 934 for selecting an angular value(e.g., not exceeding 360) for the variable azimuth position. The thirdangular component sub-module 934 using the first and second antennaazimuth gain parameter characteristics to identify the correspondingfirst and second antenna azimuth gain parameter values for the variableazimuth position associated with the selected angular value.

In this embodiment, the third angular component sub-module 934 may alsodetermine a difference between first and second transmit antenna gainsfor the selected angular value. The difference may be determined byadding the first antenna azimuth gain parameter value for the selectedangular value to the first antenna elevation gain parameter value andsubtracting the first antenna maximum gain parameter value to obtain thefirst transmit antenna gain, adding the second antenna azimuth gainparameter value for the selected angular value to the second antennaelevation gain parameter value and subtracting the second antennamaximum gain parameter value to obtain the second transmit antenna gain,and subtracting the second transmit antenna gain from the first transmitantenna gain to obtain a third angular position component.

The angular value selected for the initial variable azimuth position canbe based at least in part on knowledge of which sector antenna isserving the mobile station and the orientation and azimuth position ofthe serving sector antenna. Subsequent values selected for the variableazimuth position can be based on whether the subsequent result isapproaching or receding from the desired result. Various techniques canalso be used to select subsequent values for the variable azimuthposition based on the magnitude of the difference between the subsequentresult and the desired result as well as the change in the differencebetween consecutive subsequent results and the desired result.

For example, in a further embodiment of the angular position module 906,the angular value initially selected for the variable azimuth positionby the third angular component sub-module 934 may be between the firstand second antenna position values. In this embodiment, the initialangular value may be representative of a mid-point between the first andsecond antenna position values. In other words, if the first antenna isoriented to 120 degrees in relation to the angular reference position, asecond antenna may be oriented to 240 degrees, and 180 may be selectedas the initial angular value for the variable azimuth position becauseit is at a midpoint between the first and second sector antennas. Theselection of other angular values for the variable azimuth position cantake into account whether the results are getting better or worse toselect angular values to obtain better results. The iterative selectionof angular values can be incremental or based on a factor of thedifference between the obtained result and the desired result.

In a yet further embodiment, the angular position module 906 may includean arithmetic sub-module 942 and a control sub-module 944. In thisembodiment, the arithmetic sub-module 942 is in operative communicationwith the first, second, and third angular component modules 938, 940,934 for adding the first and third angular position components andsubtracting the second angular position component to form an arithmeticresult. In the embodiment being described, the arithmetic sub-module 942converts the arithmetic result to an absolute value. The controlsub-module 944 is in operative communication with the arithmeticsub-module 942 and the third angular component sub-module 934 foridentifying the angular value substituted for the variable azimuthposition as the current angular position for the mobile station 900 ifthe arithmetic result is within a predetermined threshold of a desiredvalue (e.g., zero). Otherwise, the control sub-module 944 may causes thethird angular component module 934 to repeat the selecting with adifferent angular value and the determining of the difference betweenthe first and second transmit gains to obtain a new value for the thirdangular position component, causes the arithmetic sub-module 942 torepeat the adding and subtracting to form the arithmetic result and thedetermining of the absolute value, and causes the repeating to continueuntil the arithmetic result is within the predetermined threshold of thedesired value.

In an alternate further embodiment, the arithmetic sub-module 942 may bein operative communication with the first, second, and third angularcomponent modules 938, 940, 934 for adding the first and third angularposition components and subtracting the second angular positioncomponent to form an arithmetic result. In the embodiment beingdescribed, the arithmetic sub-module 942 converts the arithmetic resultto an absolute value. In this embodiment, the control sub-module 944 maybe in operative communication with the arithmetic sub-module 942 and thethird angular component module 934 for causing the third angularcomponent sub-module 934 to repeat the selecting with a differentangular value and the determining of the difference between the firstand second transmit gains to obtain a new value for the third angularposition component, causing the arithmetic sub-module 942 to repeat theadding and subtracting to form the arithmetic result and the determiningof the absolute value, and causing the repeating to continue until theabsolute value is minimized. In the embodiment being described, thecontrol sub-module 944 identifies the corresponding angular valuesubstituted for the variable azimuth position for which the absolutevalue is minimized as the current angular position for the mobilestation 900.

In another alternate further embodiment, the arithmetic sub-module 942may be in operative communication with the first, second, and thirdangular component modules 938, 940, 934 for summing the first and thirdangular position components to form an arithmetic result. In theembodiment being described, the arithmetic sub-module 942 compares thearithmetic result to the second angular position component 940. In thisembodiment, the control sub-module 944 may be in operative communicationwith the arithmetic sub-module 942 and the third angular componentsub-module 934 for identifying the angular value substituted for thevariable azimuth position as the current angular position for the mobilestation if the arithmetic result is within a predetermined range of thesecond angular position component. Otherwise, the control sub-module 944causes the third angular component module 934 to repeat the selectingwith a different angular value and the determining of the differencebetween the first and second transmit gains to obtain a new value forthe third angular position component, causes the arithmetic sub-module942 to repeat the summing of the first and third angular positioncomponents to form the arithmetic result and the comparing of thearithmetic result to the second angular position component, and causethe repeating to continue until the arithmetic result is within thepredetermined range of the second angular position component.

With reference to FIG. 10, an exemplary embodiment of a non-transitorycomputer-readable medium storing program instructions that, whenexecuted by a computer, cause a corresponding computer-controlled deviceto perform a process 1000 for estimating a geographic location of amobile station within a coverage area of a wireless network. In oneembodiment, the process 1000 begins at 1002 where a radial distance of amobile station from a base station is calculated. The base stationincluding multiple sector antennas. The radial distance is based atleast in part on a round trip measurement associated with elapsed timebetween sending an outgoing signal from the base station to the mobilestation and receiving a corresponding acknowledgement signal from themobile station at the base station. At 1004, the process determines asignal strength report from the mobile station provided to the basestation includes a signal strength measurement representative of a powercharacteristic of an RF signal received by the mobile station from asector antenna of the base station. Next, an instant geographic locationof the mobile station in a coverage area of the wireless network may beidentified (1006).

In various embodiments, the program instructions stored in thenon-transitory computer-readable memory, when executed by the computer,may cause the computer-controlled device to perform various combinationsof functions associated with the various embodiments of the processes400, 500, 1700, 1800, 1900, 2000, 2100, 2200, and 2300 for estimating ageographic location of a mobile station described above with referenceto FIGS. 4, 5, and 17-23. In other words, the various embodiments of theprocesses 400, 500, 1700, 1800, 1900, 2000, 2100, 2200, and 2300described above may also be implemented by corresponding embodiments ofthe process 1000 associated with the program instructions stored in thenon-transitory computer-readable memory.

Likewise, in various embodiments, the program instructions stored in thenon-transitory computer-readable memory, when executed by the computer,may cause the computer-controlled device to perform various combinationsof functions associated with the various embodiments of the apparatusfor estimating a geographic location of a mobile station described abovewith reference to FIGS. 6-8 and the angular position module 906described above with reference to FIG. 9.

For example, the computer-controlled device may include a base station(see FIG. 6, 608), a geo-location service node (see FIG. 7, 722), anetwork management node (see FIG. 8, 828), or any suitable communicationnode associated with the wireless network. Any suitable module orsub-module described above with reference to FIGS. 6-9 may include thecomputer and non-transitory computer-readable memory associated with theprogram instructions. Alternatively, the computer and non-transitorycomputer-readable memory associated with the program instructions may beindividual or combined components that are in operative communicationwith any suitable combination of the modules and sub-modules describedabove with reference to FIGS. 6-9

The above description merely provides a disclosure of particularembodiments of the invention and is not intended for the purposes oflimiting the same thereto. As such, the invention is not limited to onlythe above-described embodiments. Rather, it is recognized that oneskilled in the art could conceive alternative embodiments that fallwithin the scope of the invention.

We claim:
 1. A method for estimating a geographic location of a mobilestation within a coverage area of a wireless network, comprising:calculating an instant angular position of an individual mobile stationin relation to a first base station, the first base station includingmultiple sector antennas, the instant angular position based at least inpart on a first signal strength measurement, a second signal strengthmeasurement, and an angular position reference that extends outward fromthe first base station, the first and second signal strengthmeasurements related in calendar time and representative of powercharacteristics of respective radio frequency (RF) signals received bythe individual mobile station from corresponding first and second sectorantennas of the first base station; determining a radial distance of theindividual mobile station from the first base station, the radialdistance based at least in part on a round trip measurement associatedwith elapsed time between sending an outgoing signal from the first basestation to the individual mobile station and receiving a correspondingacknowledgement signal from the individual mobile station at the firstbase station, the round trip measurement related in calendar time to thefirst and second signal strength measurements; and identifying aninstant geographic location of the individual mobile station in acoverage area of a wireless network formed by at least the first basestation, the instant geographic location based at least in part on anintersection of a line extending outward from the first base station atthe instant angular position with a circle having a center defined bythe first base station and a radius defined by the radial distance. 2.The method of claim 1, further comprising: correlating the instantgeographic location of the individual mobile station with a firstsub-sector geographic area in a first RF coverage map for the firstsector antenna based at least in part on a reference location for thefirst base station in the first RF coverage map, the first RF coveragemap formed by a plurality of sub-sector geographic areas, eachsub-sector geographic area uniquely identified and associated with acorresponding geographic location bin for the first RF coverage map forstorage of signal strength measurements from the first sector antennaassociated with the corresponding sub-sector geographic area; andsending the first signal strength measurement to a first geographiclocation bin associated with the unique identifier for the firstsub-sector geographic area for storage in conjunction with computationof a representative RF coverage level for populating the firstsub-sector geographic area in the first RF coverage map.
 3. The methodof claim 1, further comprising: correlating the instant geographiclocation of the individual mobile station with a second sub-sectorgeographic area in a second RF coverage map for the second sectorantenna based at least in part on a reference location for the firstbase station in the second RF coverage map, the second RF coverage mapformed by a plurality of sub-sector geographic areas, each sub-sectorgeographic area uniquely identified and associated with a correspondinggeographic location bin for the second RF coverage map for storage ofsignal strength measurements from the second sector antenna associatedwith the corresponding sub-sector geographic area; and sending thesecond signal strength measurement to a second geographic location binassociated with the unique identifier for the second sub-sectorgeographic area for storage in conjunction with computation of arepresentative RF coverage level for populating the second sub-sectorgeographic area in the second RF coverage map.
 4. The method of claim 1,the method further comprising: determining a radial distance of theindividual mobile station from a second base station serving theindividual mobile station, the second base station including multiplesector antennas, the radial distance based at least in part on a roundtrip measurement associated with elapsed time between sending anoutgoing signal from the second base station to the individual mobilestation and receiving a corresponding acknowledgement signal from theindividual mobile station at the second base station, the round tripmeasurement related in calendar time to the first and second signalstrength measurements.
 5. The method of claim 4, further comprising:identifying an instant geographic location of the individual mobilestation in a coverage area of a wireless network formed by at least thefirst and second base stations, the instant geographic location based atleast in part on an intersection of a line extending outward from thefirst base station at the instant angular position with a circle havinga center defined by the second base station and a radius defined by theradial distance.
 6. The method of claim 5 wherein a signal strengthmeasurement report from the individual mobile station comprising thefirst and second signal strength measurements also includes a thirdsignal strength measurement, the third signal strength measurementrepresentative of the power characteristic of a third RF signal receivedby the individual mobile station from a third sector antenna of thesecond base station, the method further comprising: correlating theinstant geographic location of the individual mobile station with athird sub-sector geographic area in a third RF coverage map for thethird sector antenna based at least in part on a reference location forthe second base station in the third RF coverage map, the third RFcoverage map formed by a plurality of sub-sector geographic areas, eachsub-sector geographic area uniquely identified and associated with acorresponding geographic location bin for the third RF coverage map forstorage of signal strength measurements from the third sector antennaassociated with the corresponding sub-sector geographic area; andsending the third signal strength measurement to a third geographiclocation bin associated with the unique identifier for the thirdsub-sector geographic area for storage in conjunction with computationof a representative RF coverage level for populating the thirdsub-sector geographic area in the third RF coverage map.
 7. A method forestimating a geographic location of a mobile station within a coveragearea of a wireless network, comprising: calculating a radial distance ofan individual mobile station from a first base station serving theindividual mobile station, the first base station including multiplesector antennas, the radial distance based at least in part on a roundtrip measurement associated with elapsed time between sending anoutgoing signal from the first base station to the individual mobilestation and receiving a corresponding acknowledgement signal from theindividual mobile station at the first base station; determining asignal strength report from the individual mobile station provided tothe first base station related in calendar time to the round tripmeasurement includes a first signal strength measurement representativeof a power characteristic of a first radio frequency (RF) signalreceived by the individual mobile station from a first sector antenna ofthe first base station, the signal strength report not including othersignal strength measurements for other sector antennas of the first basestation; and identifying an instant geographic location of theindividual mobile station in a coverage area of a wireless networkformed by at least the first base station, the instant geographiclocation based at least in part on an intersection of a circle having acenter defined by the first base station and a radius defined by theradial distance with a first sub-sector geographic area in a first RFcoverage map for the first sector antenna, the first RF coverage mapincluding a first reference location for the first base station tofacilitate correlation of the circle to the first RF coverage map, thefirst RF coverage map formed by a plurality of sub-sector geographicareas, the first RF coverage map populated with representative RFcoverage levels associated with previous signal strength measurementsfor the first sector antenna from one or more mobile stations inprevious signal strength reports comprising the corresponding previoussignal strength measurement and at least one signal strength measurementfrom another sector antenna of the first base station, wherein the firstsub-sector geographic area in the first RF coverage map is populatedwith a first RF coverage level representative of lacking previous signalstrength measurements.
 8. The method of claim 7 wherein each sub-sectorgeographic area is uniquely identified and associated with acorresponding geographic location bin for the first RF coverage map forstorage of previous signal strength measurements from the first sectorantenna associated with the corresponding sub-sector geographic area anda first geographic location bin associated with the first RF coveragemap and the first sub-sector geographic area is void of previous signalstrength measurements.
 9. The method of claim 8, further comprising:identifying multiple sub-sector geographic areas in the first RFcoverage map intersecting the circle associated with the first basestation that are populated with the first RF coverage level; comparingthe first signal strength measurement to representative RF coveragelevels associated with previous signal strength measurements stored incorresponding geographic location bins for corresponding sub-sectorgeographic areas of the first RF coverage map neighboring each of themultiple sub-sector geographic areas; and selecting the first sub-sectorgeographic area from the multiple sub-sector geographic areas based atleast in part on the neighboring RF coverage level for the firstsub-sector geographic area being associated with previous signalstrength measurements that are closer to the first signal strengthmeasurement than previous signal strength measurements associated withneighboring RF coverage levels for other sub-sector geographic areas ofthe multiple sub-sector geographic areas.
 10. The method of claim 8,further comprising: sending the first signal strength measurement to afirst geographic location bin associated with the unique identifier forthe first sub-sector geographic area for storage in conjunction withcomputation of a representative RF coverage level for populating thefirst sub-sector geographic area in a second RF coverage map for thefirst sector antenna, the second RF coverage map formed by a pluralityof sub-sector geographic areas, the second RF coverage map populatedwith representative RF coverage levels associated with previous signalstrength measurements for the first sector antenna from one or moremobile stations in previous signal strength reports.
 11. The method ofclaim 7, further comprising: determining the signal strength report fromthe individual mobile station provided to the first base stationincludes a second signal strength measurement representative of thepower characteristic of a second RF signal received by the individualmobile station from a second sector antenna of a second base station,the second base station including multiple sector antennas.
 12. Themethod of claim 11 wherein the first RF coverage map includes a secondreference location for the second base station, the method furthercomprising: identifying multiple sub-sector geographic areas in thefirst RF coverage map intersecting the circle associated with the firstbase station that are populated with the first RF coverage level;comparing geographic locations of the multiple sub-sector geographicareas in the first RF coverage map to a fixed location for the secondbase station in relation to the first RF coverage map; and selecting thefirst sub-sector geographic area from the multiple sub-sector geographicareas based at least in part on the geographic location for the firstsub-sector geographic area being closer to the fixed location for thesecond base station than the geographic locations for other sub-sectorgeographic areas of the multiple sub-sector geographic areas.
 13. Themethod of claim 11, further comprising: correlating the instantgeographic location of the individual mobile station with a secondsub-sector geographic area in a second RF coverage map for the secondsector antenna based at least in part on a second reference location forthe first base station in the second RF coverage map, the second RFcoverage map formed by a plurality of sub-sector geographic areas, eachsub-sector geographic area uniquely identified and associated with acorresponding geographic location bin for the second RF coverage map forstorage of signal strength measurements from the second sector antennaassociated with the corresponding sub-sector geographic area; andsending the second signal strength measurement to a second geographiclocation bin associated with the unique identifier for the secondsub-sector geographic area for storage in conjunction with computationof a representative RF coverage level for populating the secondsub-sector geographic area in the second RF coverage map for the secondsector antenna.
 14. A method for estimating a geographic location of amobile station within a coverage area of a wireless network, comprising:calculating an instant angular position of an individual mobile stationin relation to a first base station, the first base station includingmultiple sector antennas, the instant angular position based at least inpart on a first signal strength measurement, a second signal strengthmeasurement, and an angular position reference that extends outward fromthe first base station, the first and second signal strengthmeasurements related in calendar time and representative of powercharacteristics of respective radio frequency (RF) signals received bythe individual mobile station from corresponding first and second sectorantennas of the first base station; determining a radial distance of theindividual mobile station from a second base station serving theindividual mobile station, the second base station including multiplesector antennas, the radial distance based at least in part on a roundtrip measurement associated with elapsed time between sending anoutgoing signal from the second base station to the individual mobilestation and receiving a corresponding acknowledgement signal from theindividual mobile station at the second base station, the round tripmeasurement related in calendar time to the first and second signalstrength measurements; and identifying an instant geographic location ofthe individual mobile station in a coverage area of a wireless networkformed by at least the first and second base stations, the instantgeographic location based at least in part on an intersection of a lineextending outward from the first base station at the instant angularposition with a circle having a center defined by the second basestation and a radius defined by the radial distance.
 15. The method ofclaim 14 wherein the first base station is serving the individual mobilestation, the method further comprising: determining a radial distance ofthe individual mobile station from the first base station, the radialdistance based at least in part on a round trip measurement associatedwith elapsed time between sending an outgoing signal from the first basestation to the individual mobile station and receiving a correspondingacknowledgement signal from the individual mobile station at the firstbase station, the round trip measurement related in calendar time to thefirst and second signal strength measurements.
 16. The method of claim15, further comprising: identifying an instant geographic location ofthe individual mobile station in a coverage area of a wireless networkformed by at least the first base station, the instant geographiclocation based at least in part on an intersection of a line extendingoutward from the first base station at the instant angular position witha circle having a center defined by the first base station and a radiusdefined by the radial distance.
 17. The method of claim 16, furthercomprising: correlating the instant geographic location of theindividual mobile station with a first sub-sector geographic area in afirst RF coverage map for the first sector antenna based at least inpart on a reference location for the first base station in the first RFcoverage map, the first RF coverage map formed by a plurality ofsub-sector geographic areas, each sub-sector geographic area uniquelyidentified and associated with a corresponding geographic location binfor the first RF coverage map for storage of signal strengthmeasurements from the first sector antenna associated with thecorresponding sub-sector geographic area; and sending the first signalstrength measurement to a first geographic location bin associated withthe unique identifier for the first sub-sector geographic area forstorage in conjunction with computation of a representative RF coveragelevel for populating the first sub-sector geographic area in the firstRF coverage map.
 18. The method of claim 16, further comprising:correlating the instant geographic location of the individual mobilestation with a second sub-sector geographic area in a second RF coveragemap for the second sector antenna based at least in part on a referencelocation for the first base station in the second RF coverage map, thesecond RF coverage map formed by a plurality of sub-sector geographicareas, each sub-sector geographic area uniquely identified andassociated with a corresponding geographic location bin for the secondRF coverage map for storage of signal strength measurements from thesecond sector antenna associated with the corresponding sub-sectorgeographic area; and sending the second signal strength measurement to asecond geographic location bin associated with the unique identifier forthe second sub-sector geographic area for storage in conjunction withcomputation of a representative RF coverage level for populating thesecond sub-sector geographic area in the second RF coverage map.
 19. Themethod of claim 14 wherein a signal strength measurement report from theindividual mobile station comprising the first and second signalstrength measurements also includes a third signal strength measurement,the third signal strength measurement representative of the powercharacteristic of a third RF signal received by the individual mobilestation from a third sector antenna of the second base station, themethod further comprising: correlating the instant geographic locationof the individual mobile station with a third sub-sector geographic areain a third RF coverage map for the third sector antenna based at leastin part on a reference location for the second base station in the thirdRF coverage map, the third RF coverage map formed by a plurality ofsub-sector geographic areas, each sub-sector geographic area uniquelyidentified and associated with a corresponding geographic location binfor the third RF coverage map for storage of signal strengthmeasurements from the third sector antenna associated with thecorresponding sub-sector geographic area; and sending the third signalstrength measurement to a third geographic location bin associated withthe unique identifier for the third sub-sector geographic area forstorage in conjunction with computation of a representative RF coveragelevel for populating the third sub-sector geographic area in the thirdRF coverage map.